1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to a cooling fan for a thermal printing head used in a thermal printer.
2. Description of the Related Art
Thermal printers are generally one of two types of printer. The first type has an ink ribbon made of a film substrate that contacts printing media with a predetermined pressure. Ink coated on the ink ribbon is heated to transfer the ink onto the printing media. The other type of printer uses a thermal sensitive printing media. Ink layers on the media are heated by induction to reveal the ink, which is made of predetermined colors.
A thermal printing head (TPH) is used to apply heat to the ink ribbon or the thermal sensitive printing media. A TPH includes a plurality of heating elements that can be separately controlled and are disposed at predetermined intervals. The quality of an image formed by a thermal image forming apparatus depends on the temperature of the TPH. For example, after images are printed on a line, the TPH has to be quickly cooled so that print images can be printed on the next line. Also, since the temperature of the central portion of the TPH is generally higher than the temperature of the edge portions of the TPH, the TPH has to be cooled to make the temperature uniform over the entire TPH. Otherwise, image quality deteriorates due to residual heat of the TPH.
Japanese Laid-Open Patent Application No. JP2003-341115, the entire disclosure of which is hereby incorporated by reference, discloses a structure that circulates air in an image forming apparatus with a fan to cool a TPH. However, circulating air within an image forming apparatus is not as efficient as directly supplying air to cool the TPH.
Japanese Laid-Open Patent Application No. JP2001-260479, the entire disclosure of which is hereby incorporated by reference, discloses a fan installed above a TPH to directly supply air to cool the TPH. Some thermal printers, however, rotate the TPH between two positions to print on first and second surfaces of a printing medium. The disclosed structure is not suitable for use with such a thermal printer.
Accordingly, there is a need for an improved apparatus for cooling a TPH, and an image forming apparatus employing the same.